Friday 9 January 2009 19.01 EST
First published on Friday 9 January 2009 19.01 EST

Until Victoria Pendleton punched me last year I thought I had a justified, if predictable, excuse for not doing enough exercise in 2008. I regularly trotted out the lazy old line that I was too busy to go for a run or a swim or to even think about opening a shiny catalogue offering membership to some swanky new gym. At least I could put a vaguely novel twist on an unoriginal claim by suggesting I was too preoccupied, listening to people tell me how compulsively they trained, to do any exercise myself.

These were not typical people, after all, but a series of Olympic medal-winning British athletes whom I interviewed for the Guardian. Pendleton, the sprint-cyclist who won gold in Beijing, offered one of my more memorable encounters in a string of interviews with bike-riders, runners, rowers, swimmers, gymnasts, boxers and various other supremely fit athletes before and after last summer's Olympics. For a while it seemed as if I did little else but nod approvingly as one dedicated Olympian after another told me how they had honed their bodies relentlessly.

They were different to most other famous sporting figures. For a start they trained far harder and earned much less money than their glittering counterparts in mainstream professional sports such as football. And curiously, apart from the crucial fact that they were so intensely disciplined, they turned out to be as relatively ordinary as the rest of us. They actually lived in the real world.

In between hearing their stories of monstrous training regimes, I liked talking to them about what sort of biscuits they missed eating, what books they liked to read, how much they drank when they celebrated their sporting success - and why they were driven to sacrifice themselves to Olympic ambition.

In the course of one such conversation with Pendleton, who was unflinchingly honest, whether analysing her love-life or the fear of sporting failure, she said with thrilling urgency: "I don't think I could live without strenuous exercise." I must have looked mildly glazed because she followed it up with a redundant question: "Could you?"

It did not take long for her to laugh out loud. I offered sizeable proof that it was possible to live, just about, without strenuous exercise. And so I explained that I'm imaginative enough to consider cracking open another bottle of red wine as a form of exercise. And that was when Pendleton punched me - a jokey but firmly-toned blow on my upper arm - and made me listen more seriously as she described why physical fitness matters. "There are enough challenges in real life, and demons in our head, that it helps to take charge of our physical condition. I have to do that as an Olympic cyclist, but I also want to do it as someone who can still feel insecure."

A hard candour ran through Pendleton; and she was at her most compelling when, addressing her vulnerabilities, she explained how exercise transformed her. "When I first came to the Manchester Velodrome [the headquarters of British cycling] I was a shy work-experience student. But I hardly ever went into the office.

I trained my heart out. I wanted to become good at something. The male cyclists were dubious but, training hard, I gained respect. It's a feeling everyone can experience - because we can all exercise at our own level of fitness. That's the beauty of exercise. It can change your life."

I liked the way in which exercise saved Louis Smith, the first British man to win an Olympic medal in gymnastics in 100 years. His unexpected bronze on the pommel horse in Beijing completed a journey that began on a council estate in Peterborough. As a hyperactive boy, Smith was dismissed as a "problem-child". He was said to suffer from an untreatable attention deficit hyperactivity disorder. "I was lost in my chaotic world then," Smith told me. "People thought I was stupid."

Smith's mother, Elaine, believed differently. She took him to a gymnasium and, as Smith recalls: "My coach channelled my energy into exercise. He started saying nice things like I was very intelligent. Exercise gave me that."

Even a muscled 19-year-old such as Smith has days like the rest of us. At his first training session after the Olympics, "It felt like my body was falling apart, like I was 40 years old, like someone ancient." I nodded knowingly. Smith also explained how he had won his Olympic medal despite training alongside toddler groups at a cramped gym in Huntingdon. "We'd be trying to do double somersaults and a tiny kid would run into our path and we'd shout 'Stop!' in case we killed them. But we kept training - because you always can, whether you're going for the Olympics or just keeping fit. If you put your mind to it you can do anything."

That stern advice from a tattooed teenager cannot be ignored. I also remember the profound hour I shared with Christine Ohuruogu just before she won Olympic gold in the 400m. Ohuruogu said lightly that, "if you set your sights on something, and keep your eyes on that goal, so much is achievable in life. It might be a case of wanting to get a new job or becoming fitter than you've been. If you stay calm and determined it's always possible. That's what I'm trying to do now. I think I can win but it's all about focus - and maintaining balance. There are other parts of our body we need to exercise as well."

"Like what?" I asked dumbly.

"Like our brains," Ohuruogu said sweetly. "I love reading ..."

Reading as exercise, with a performance-enhancing glass of red wine at my side, will form part of my own keep-fit campaign. But I also came away from my illuminating encounters with some of Britain's best Olympians with a new respect for the gym, bike, pool and track. And as impossible as it would be to try and keep up with Pendleton, Smith, Ohuruogu and all those other impressively concentrated Olympians, it's easy to recall the cyclist replacing my old excuse for not doing enough exercise with just a few helpful words.

"It's basic stuff," Pendleton said, "that we can all do. You just need to go for a little run down the road or a swim in your local pool. Or you can visit the gym or hop on a bike for a ride. You won't need to do more than 20 minutes a day to feel miles better about yourself. It's that simple."